PROJECT SUMMARY Cholera is an acute and severe disease caused by the bacterium Vibrio cholerae that is spread primarily through contaminated water sources due to a lack of adequate sanitation infrastructure. The World Health Organization estimates that there are at least 3 million cases globally per year, 40 percent of which are spread through household transmission. Current prevention methods require significant investment of resources and time for efficacy, but household contacts of cholera patients often present with cholera symptoms two to three days after the initial patient becomes sick. In addition, the preventive use of antibiotics is not recommended due to widespread resistance and the known negative consequences of dysbiosis. There is a pressing need to develop a targeted clinical intervention to prevent the community spread of cholera using a rapid prophylactic treatment. The goal of the proposed studies is to demonstrate feasibility of developing our phage-based clinical intervention, ProphaLytic-VC, to prevent the community spread of cholera. ProphaLytic-VC is an orally administered cocktail of three different phages known as ICP1, ICP2, and ICP3. To date, these are the only three virulent phages found in association with epidemic strains of cholera. Detailed genomic and phenotypic characterization each of the phages has been conducted by the academic partner, resulting in genome sequences, annotation, and identification of the host receptors. The combination of the three has been evaluated to demonstrate potency in reducing colonization of V. cholerae and prevention of cholera symptoms in two animal models of V. cholerae colonization and pathogenesis. Here, we propose studies to optimize a robust and scalable manufacturing process for ProphaLytic-VC, as there is currently little manufacturing experience in the USA due to the novel nature of the product. We will construct two phage production strains, develop a scalable phage production and purification scheme, and evaluate any potential local of systemic toxicity. At the successful conclusion of Phase I, we will have a resultant Master Phage Stock (MPS) of ProphaLytic-VC from an optimized large-scale production scheme that is potent against V. cholerae and safe with repeated oral administration. STTR Phase II funding will be used to fund further activities to generate a working phage seed stock from the MPS to proceed with a Phase I clinical trial.